190 Scheerer on Isomorphism. 
number of proofs we have adduced thereof, we are fully borne out 
in doing, we obtain an oxygen ratio of 17-47 P: 17°53 (Fe), cor- 
responding with almost mathematical aceuracy to the simple for- 
mula (Fe)° P, and in which formula base and acid contain equal 
amounts of oxygen 
2. Earthy Vivianite, from Hillentrup. 
ayer consists, according to an analysis of Brandes, of phospho- 
d 30-320, Saget ie of iron 43:775, water 25° 000, alumina 
0: 700, silica 0-025 = 99-820. 
The oxygen ratio deieiod herefrom is as follows: 18:60: 17°38. 
Deducting the alumina as a phosphate, the ratio becomes even 
more nearly 1; 1, whence we also obtain for this mineral t6o the 
formula (Fe) P. 
3. Vivianite, from Bodenmais. 
Vogel’s analysis gave, phosphoric acid 26:4, protoxyd of iron 
41‘0, water 31:0=98:- 
If we may rely on ‘6 sstiee de of this result, it will justify 
the nem formula, ( Fe) Pi5H 
e oxygen ratio as it may be calculated from the result of 
the analysis, is, 14: 79P : 14 00(Fe) : 13-58% 
should be 1400 :1400  ; 14-00. 
A portion of the water in this mineral is basic, another portion 
exists as a hydrate. ‘The formula thus resulting for the Boden- 
mais vivianite, is ed similar to that which we obtain upon 
converting, on the principle here involved, the formula of the 
artificially prepared hydrous phosphate of magnesia, which is 
Mg? P+-14H, whereby we obtain (Mg)° P+5H 
The corresponding artificial salts of the anasyd of iron and 
of the protoxyd of manganese, have not as yet been analyzed, 
but without a doubt the same formula is also applicable to them. 
It would however be well to submit the enmais vivianite to 
a further examination in order to ascertain with certainty whether 
in point of fact its composition is different from that from Cornwall, 
which as the two minerals agree in their crystalline form is cer- 
tainly not probable. 
4. Mullicite. 
Thompson obtained for the composition of this mineral, fer ee 
phoric acid 26:06, protoxyd of iron 46:31, water 27° 1499 
The corresponding oxygen ratio is, 14: 60 P : 14-00 (Fe): 
13 75H, which gives as the fonpale 2 mullicite (Fe)'P+5H, 
